Organic light emitting diode (OLED) is one of the research focuses in the field of display. Compared with liquid crystal displays (LCDs), OLEDs have the advantages of low energy consumption, low production cost, self-illuminating, wide viewing angle and fast response speed, etc. Currently, in the fields such as mobile phones, Personal Digital Assistants (PDAs) and digital cameras, OLED display screens have begun to replace traditional LCD display screens. Pixel circuit design is the core technology of the OLED display, and has important research significance.
Unlike LCDs utilizing stable voltages to control the brightness, OLEDs are driven by currents and require stable currents to control light emitting. Due to manufacturing processes, the aging of devices and so on, the threshold voltages Vth of drive transistors of the pixel circuit are different, thereby resulting in the differences in currents flowing through different OLED pixels, which causes different display brightness and thus affects the display effect of the whole image.
For example, it is possible to decrease the difference in brightness by arranging more transistors, which, however, would decrease the aperture ratio and is disadvantageous for high-resolution display.